#include <iostream>
using namespace std;

class Solution {
public:
    string modifyString(string s)
    {
        int n = s.size();
        for (int i = 0; i < n; ++i)
        {
            if (s[i] == '?')
            {
                for (char ch = 'a'; ch <= 'z'; ++ch)
                {
                    if ((i == 0 || ch != s[i - 1]) && (i == n - 1 || ch != s[i + 1]))
                    {
                        s[i] = ch;
                        break;
                    }
                }
            }
        }
        return s;
    }
};

int main()
{
    Solution();

    return 0;
}